Conventional articles of athletic footwear include two primary elements, an upper and a sole structure. The upper provides a covering for the foot that comfortably receives and securely positions the foot with respect to the sole structure. The sole structure is secured to a lower portion of the upper and is generally positioned between the foot and the ground. In addition to attenuating ground reaction forces (i.e., providing cushioning) during walking, running, and other ambulatory activities, the sole structure may influence foot motions (e.g., by resisting pronation), impart stability, and provide traction, for example. Accordingly, the upper and the sole structure operate cooperatively to provide a comfortable structure that is suited for a wide variety of athletic activities.
The upper is often formed from a plurality of material elements (e.g., textiles, polymer sheets, foam layers, leather, synthetic leather) that are stitched or adhesively bonded together to form a void on the interior of the footwear for comfortably and securely receiving a foot. More particularly, the upper forms a structure that extends over instep and toe areas of the foot, along medial and lateral sides of the foot, and around a heel area of the foot. The upper may also incorporate a lacing system to adjust fit of the footwear, as well as permitting entry and removal of the foot from the void within the upper. In addition, the upper may include a tongue that extends under the lacing system to enhance adjustability and comfort of the footwear, and the upper may incorporate a heel counter.
The sole structure generally incorporates multiple layers: a sockliner, a midsole, and an outsole. The sockliner is a thin, compressible member located within the upper and adjacent to a plantar (i.e., lower) surface of the foot to enhance footwear comfort. The midsole is secured to a lower surface of the upper and forms a middle layer of the sole structure. Many midsole configurations are primarily formed from a resilient polymer foam material, such as polyurethane or ethylvinylacetate, that extends throughout the length and width of the footwear. The midsole may also incorporate fluid-filled chambers, plates, moderators, or other elements that further attenuate forces, influence the motions of the foot, or impart stability, for example. The outsole forms the ground-contacting element of the footwear and may be fashioned from a durable and wear-resistant material (e.g., rubber) that includes texturing to improve traction.